1. Field of the Invention
This invention relates to a power conversion device for a solar cell. More particularly, this invention relates to a power conversion device for a solar cell which can draw from the solar cell the maximum electric power corresponding to the amount of sunlight impinging upon the solar cell and can establish interconnection between the solar cell and a commercial ac power source.
2. Description of the Prior Art
Solar cells, as widely known, are designed to absorb sunlight and generate electric current. The generated electric current or electric power, therefore, varies with the varying amount of sunlight impinging upon the solar cell. During the night, no electric power can be drawn from the solar cell.
In the solar cell power source systems which have been reduced to practical utility, therefore, it is customary that they are combined with secondary batteries to form so-called floating charging circuits. In this construction, since the secondary batteries are charged during the daytime generally abundant with sunlight, necessary electric power can be drawn from them even during the night or on rainy or cloudy days deficient in sunlight.
In the conventional system, when the lead battery which has found popular use is adopted as the secondary battery, it not merely entails the danger due to the generation of hydrogen gas and oxygen gas but also necessitates maintenance such as replenishment of electrolyte. The lead battery, therefore, has a disadvantage that it cannot be utilized in such a small power system as owned by any household power consumer.
Storage batteries of other types are expensive and possess no ample capacity.
Further, since the commercial power source (100/200 V, 50/60 cycles) is widely used for various kinds of devices or equipments, the solar cell system is desired to be capable of connection to the commercial power source.
This interconnection, however, proves disadvantageous in respect that it necessitates additional incorporation of an inverter, for example, and inevitably complicates the mechanism, increases the size, and adds to the cost of equipment.